As shown in Japanese Patent No. 3252133, for example, this type of connector for memory card comprises a housing on which an opening is provided on a front face so as to insert a memory card therein, a plurality of contacts that is held in the housing and in contact with terminals provided on the memory card, a slider that contacts with the memory card inserted into the housing and is moved along an inserting direction of the memory card into the housing, a pressing spring for pressing the slider in a direction of taking out the memory card, and a push-on and push-off locking mechanism that locks movement of the slider when the slider is moved to a locking position inner than a position at which the terminals of the memory card come into contact with the contacts and releases locking of the slider when the slider is moved to a lock releasing position inner than the locking position.
In such a connector for memory card having the push-on and push-off locking mechanism, when the memory card is inserted into the housing from the opening thereof, a front end of the memory card engages with the slider, and the slider together with the memory card starts to move in the housing in a direction opposing to the opening. Following to the movement of the slider, the pressing spring is charged. When the slider is moved to the locking position slightly inner than a position at which the terminals provided in the vicinity of the front end of the memory card come into contact with the contacts, the movement of the slider is locked by the locking mechanism, and in spite of the pressing force of the pressing spring, the slider and the memory card engaged therewith remain at the locking position even after pressing force applied to the memory card is removed. To take out the memory card from the connector, the memory card is further pushed into the housing for moving the slider to the position slightly inner than the locking position. Then, the locking of the slider by the locking mechanism is released, and the slider and the memory card engaged therewith are moved toward the side of the opening of the housing by the pressing force of the pressing spring. Then, since a rear end of the memory card is greatly protruded outward from the opening of the housing, the memory card can be taken out from the connector.
When the pressing force of the pressing spring is too strong, the memory card may bounce out from the housing with great force, and the memory card may be damaged due to falling. On the contrary, when the pressing force of the pressing spring is too weak, the pressing force may become weaker than frictional force caused by contact pressure of the contacts against the terminals of the memory card or the like, so that the slider and the memory card engaged therewith may be stopped before departing the terminals of the memory card from the contacts, resulting insufficient operation. Accordingly, it is impossible to make the pressing force of the pressing spring be equal to or smaller than a certain constant value, and an independent mechanism for preventing the bounce-out of the memory card is required.
On the other hand, there are some connectors for memory card each having a detection switch for detecting insertion of the memory card built-in. FIG. 12A to FIG. 12D show a configuration of a detection switch in a connector for mini SD card. In the connector for mini SD card, it is required to reduce overall depth of the housing as smaller as possible. Thus, as shown in the figures, a fixed contact plate 30 and a movable spring piece 31 that constitute the detection switch are provided integrally with a base member 7 of a contact block for holding a plurality of contacts by insert molding. The fixed contact plate 30 is provided at a protruding portion 71 formed so as to protrude forward from an end of the base member 7 of the contact block, and a fixed contact 30a is exposed to the inner side of the connector in the width direction from the protruding portion 71 so as to contact with an elastic contact portion 31a of the movable spring piece 31. Furthermore, the movable spring piece 31 is formed so that the elastic contact portion 31a is inclined with respect to the inserting direction of the memory card so as to come into contact with a front end of the memory card and to be deformed toward the side of the fixed contact 30a when the memory card is inserted.
When the memory card is not inserted into the connector, the movable spring piece 31 returns to an initial state shown in FIG. 12B due to the elastic force thereof, so that the elastic contact portion 31a is departed from the fixed contact 30a. On the other hand, when the memory card is inserted into the connector, the elastic contact portion 31a of the movable spring piece 31 is bent toward the side of the fixed contact 30a by the front end of the memory card, so that the elastic contact portion 31a and the fixed contact 30a contact with each other. By applying a predetermined voltage between the fixed contact plate 30 and the movable spring piece 31, the detection switch comprised of the fixed contact plate 30 and the movable spring piece 31 is turned on/off depending on contact/non-contact of the elastic contact portion 31a of the movable spring piece 31 with the fixed contact 30a, so that it is possible to detect whether the memory card is inserted or the memory card is not inserted.
The fixed contact plate 30 is formed by pressing a metal thin plate, and the fixed contact 30a comes into contact with the elastic contact portion of the movable spring piece 31 at an end face thereof punched out by pressing. The movable spring piece 31 is also formed by pressing a metal thin plate, and the elastic contact portion 31a comes into contact with the fixed contact 30a at a surface of the metal thin plate as a material thereof. However, the elastic contact portion 31a is formed so as to protrude forward from the base member 7 in the inserting direction of the memory card, to be continued to a clank portion 31b formed closer to the side of the fixed contact plate 30 in the width direction and to form a predetermined angle with respect to the direction of inserting the memory card. Thus, the position of the elastic contact portion 31a with respect to the fixed contact 30a is easily affected by working error of the elastic contact portion 31a itself, clank portion 31b or the like. Thus, when the position of the elastic contact portion 31a shifts in the thickness direction of the connector as shown by one dotted chain line in FIG. 12A, there is a problem that the elastic contact portion 31a cannot contact with the fixed contact 30a and stability of the detection switch cannot be ensured.
Furthermore, in order to manufacture the contact block at low costs, a plurality of the contacts, the fixed contact plate 30 and the movable spring piece 31 are formed so as to be connected to each other via a connecting portion by punching and bending a piece of metal thin plate by pressing, and after insert molding the base member 7 in this state, the connecting portion is cut to separate the contacts, the fixed contact plate 30 and the movable spring piece 31 from each other. Since the contacts, the fixed contact plate 30 and the movable spring piece 31 are formed of the same plate in this manner, their thicknesses are the same.
Hereupon, to ensure strength of the portions which are insert-molded with the base member 7, it is necessary to use a metal thin plate having a certain degree of thickness (for example, 0.2 mm). Thus, the thickness of the elastic contact portion 31a becomes thicker more than requires, thereby causing problems that contact pressure between the elastic contact portion 31a and the fixed contact 30a becomes too high, permanent set occurs in the elastic contact portion 31a or a scratch is generated in the memory card that contacts with the elastic contact portion 31a when the memory card is inserted.
Besides, tolerance of width dimension of the memory card is ±0.1 mm. Therefore, results of analysis of the contact pressure in the cases where the width dimension of the memory card is +0.1 mm from a reference dimension, equal to the reference dimension and −0.1 mm from the reference dimension are shown FIGS. 13A to 13C.
As the width of the memory card is wider, an amount of bending of the movable spring piece 31 becomes larger, and accordingly the contact pressure between the elastic contact portion 31a and the fixed contact 30a also increases. When the width of the memory card was equal to the reference dimension, the contact pressure between the elastic contact portion 31a and the fixed contact 30a was 4.27 N. When the width of the memory card was larger by 0.1 mm than the reference dimension, the contact pressure between the elastic contact portion 31a and the fixed contact 30a is 4.27 N or more. When the width of the memory card was narrower by 0.1 mm than the reference dimension, the contact pressure between the elastic contact portion 31a and the fixed contact 30a was 3.56 N. In either case, since the contact pressure between the elastic contact portion 31a and the fixed contact 30a was too high, stress applied to the movable spring piece 31 became 980 N/mm2 or more, so that weakening (permanent set) occurred in the movable spring piece 31.